The present invention relates to an apparatus for heating the adhesive-coated seam portions of cans of square cross-section carried by conveyor means, and more particularly to an apparatus of the character which can supply heated air through a narrow air-passage formed by two plate members located opposite the seam portions so that the adhesive material applied to the seam portions can be melted to hermetically seal the cans.
Conventional large-capacity sheet metal cans or containers of square cross-section, usually known as 16-liter cans, have the side seam and curled peripheral end seam thereof hermetically joined by soldering means. It is known that the use of solder complicates the soldering process itself, and makes it difficult to dispose of the water used for washing the soldered cans because of the presence of metal grains in the water.
There is also known a non-soldering process developed hereto for tightly joining the seam portions. In accordance with the known non-soldering process, heat treatment is provided for heating the adhesive-coated seams of a formed container and melting the adhesive material so that it can expand uniformly all over the seams, and pinholes and other tiny punctures that may damage the airtightness of the container can be eliminated. However, this presents disadvantages from the standpoint of heat efficiency and fuel economy, since the heater is provided for heating the whole container, but not locally.
The present invention has overcome the above disadvantages of heat efficiency and fuel economy, and provides heating means by which only the seam portions of containers carried by conveyer means at very high speeds can be heated to a proper temperature.